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CH-46 Sea Knight

The Boeing CH-46 Sea Knight is a medium-lift tandem rotor cargo helicopter, used by the United States Marine Corps (USMC) to provide all-weather, day-or-night assault transport of combat troops, supplies and equipment. Assault Support is its primary function, and the movement of supplies and equipment is secondary. Additional tasks include combat support, search and rescue, support for forward refueling and rearming points, CASEVAC and Tactical Recovery of Aircraft and Personnel (TRAP). The commercial version is the BV 107-II, commonly referred to as simply the "Vertol".

Development

Piasecki was a pioneering developer of tandem-rotor helicopters, with the most famous previous helicopter being the H-21 "Flying Banana". Piasecki's former company Vertol began work on a new tandem rotor helicopter designated the Vertol Model 107 or V-107 in 1957. The V-107 had two Lycoming T53 turboshaft engines, producing 860 shp (640 kW) each. The first flight of the V-107 took place on April 22, 1958. The V-107 was then put through a flight demonstration tour in the US and overseas. In June 1958, the US Army awarded a contract to Vertol for ten production aircraft designated "YHC-1A".

The order was later decreased to three, so the Army could divert funds to the V-114, also a turbine powered tandem, but larger than the V-107. The Army's three YHC-1As were powered by GE-T-58 engines. The YHC-1As first flew in August 1959, and were followed by an improved commercial/export model, the 107-II. During 1960, the U.S. Marine Corps (USMC) evolved a requirement for a twin-turbine troop/cargo assault helicopter to replace the piston engine types then in use. Following a design competition, Boeing Vertol was selected to build its model 107M as the HRB-1, early in 1961. Boeing had acquired Vertol in 1960 and renamed the group Boeing Vertol.

The helicopter was first procured in 1961 to meet the medium-lift requirements of the Marine Corps. Its first flight in August 1962 was followed by a change in designation to CH-46A. Fleet introduction of CH-46As with the Marines and the Navy's UH-46As in November 1964. The UH-46A variant was modified for use in the vertical replenishment role. The CH-46A was equipped with a pair of T58-GE8-8B turboshaft engines rated at 1,250 shp (930 kW) each and could carry 17 passengers or 4,000 pounds (1,815 kg) of cargo. The USMC received 160 CH-46As and the US Navy acquired 24 UH-46As.

Production of the improved CH-46D followed with deliveries beginning in 1966. Its improvements included modified rotor blades and more powerful T58-GE-10 turboshaft engines rated at each. The increased power allowed the D-model to carry 25 troop or of cargo. A total of 266 CH-46Ds were produced. Also, approximately 12 CH-46As were upgraded to CH-46Ds. The Navy received 10 UH-46Ds for ship resupply.

The Marines also received 174 CH-46Fs from 1968 to 1971. The F-model retained the D-model's T58-GE-10 engines but revised the avionics and included other modifications. The CH-46F was the final production model with the last helicopter being the 524th H-46 produced. The Sea Knight has undergone upgrades and modifications. Most USMC Sea Knights were upgraded to CH-46E standard. The CH-46E features fiberglass rotor blades, airframe reinforcement, and further uprated T58-GE-16 engines producing each. Some CH-46Es have been given doubled fuel capacity. The Dynamic Component Upgrade (DCU) incorporated starting in the mid-1990s provides for increased capabilities through strengthened drive systems and rotor controls.

The commercial variant, the BV 107-II, was first ordered by New York Airways in 1960. They took delivery of their first three aircraft, configured for 25 passengers, in July 1962.

In 1965, Boeing Vertol sold the manufacturing rights of the 107 to Kawasaki Heavy Industries. Under this arrangement, all Model 107 civilian and military aircraft built in Japan are known as KV 107.

Design

The CH-46 has tandem contrarotating rotors that were powered by two GE T58 turboshaft engines. The engines are mounted on each side of the rear rotor pedestal with a driveshaft to the forward rotor. The engines are coupled so either could power both rotors in an emergency. The rotors feature three blades and could be folded for on-ship operations.

The CH-46 has a cargo bay with a rear loading ramp that could be removed or left open in flight for extended cargo or for parachute drops. A belly sling hook could be attached for carrying external cargo. It has a crew of three. A pintle-mounted 0.50 in (12.7 mm) Browning machine gun was mounted on each side of the helicopter for self-defense. Service in southeast Asia resulted in the addition of armor with the guns.

The CH-46 has fixed tricycle landing gear, with twin wheels on all three units. The gear configuration causes a nose-up stance to facilitate cargo loading and unloading. The main gear are fitted in rear sponsons that also contained fuel tanks with a total capacity of 350 US gallons (1,438 L).

Operational history

Military

Known colloquially as the "Phrog", and used in all Marine combat and peacetime environments since its introduction. Still regularly flown by the Marine Corps, its longevity as a reliable airframe has led to such mantras as "phrogs phorever" and "never trust a helicopter under 30".

CH-46E Sea Knights were used by the USMC during its 2003 invasion of Iraq. CH-46Es transported personnel, brought supplies to forward arming and refueling points (FARP), carried ammunition and various tasks. Marine CH-46Es and CH-53Es carried US Army Rangers and Special Operations troops in a mission to rescue captured Army Private Jessica Lynch on 1 April 2003.

While the United States Navy retired the airframe on September 24, 2004, replacing it with the MH-60S Knighthawk, the Marine Corps plans to maintain its fleet until the MV-22 is fully fielded. In March 2006 Marine Medium Helicopter Squadron 263 (HMM-263) was deactivated and redesignated VMM-263 to serve as the first MV-22 squadron. The replacement process is expected to continue through the other medium helicopter squadrons into 2014.

Variants

US versions

Total U.S. H-46 production amounted to 524, ending in 1971.Model 107 : Company model number.Model 107-II : The third YHC-1 prototype was converted into a commercial airline helicopter. All subsequent commercial aircraft were produced as BV 107-II.Model 107M : Military transport prototype for the United States Marine Corps.YHC-1A : Three Model 107s for test and evaluation by the United States Army. Adopted by the United States Marine Corps as the HRB-1. Later redesignated YCH-46C. Three built.YHC-1B : Were not Model 107s but five Model 114s that later became the CH-47A ChinookHRB-1 : Original designation before being renamed as CH-46A before delivery under the 1962 United States Tri-Service aircraft designation systemCH-46A : Assault, utility medium transport and SAR helicopter for the USMC, fitted with two 935-kW (1,250-shp) General Electric T58-GE-8 turboshaft engines. (Previously HRB-1). 164 built.UH-46A : Utility medium transport helicopter for the United States Navy. Similar to the CH-46A. 14 built.HH-46A : A small number of HH-46As were converted into SAR helicopters for the United States Navy base rescue role.RH-46A : A small number of CH-46As were converted into minesweeping helicopters for the US Navy.UH-46B : Development of the CH-46A to specification HX/H2 for the United States Air Force; cancelledYCH-46C :YHC-1A redesignated in 1962.CH-46D : Assault and utility medium transport helicopter for the USMC, fitted with two 1044-kW (1,400-shp) General Electric T58-GE-10 turboshaft engines. 266 built.HH-46D : A small number of UH-46Ds were converted into SAR helicopters.UH-46D : Utility transport helicopter for the US Navy combat supply role. Similar to the CH-46D. 10 built and one conversion from CH-46D.CH-46E : Approximately 350 -D and -F airframes were updated to CH-46E standards with improved avionics, hydraulics, drive train and upgraded T58-GE-16 engines.HH-46E : A small number of CH-46Es were converted into SAR helicopters.CH-46F : Improved version of CH-46D, electrical distribution, com/nav update BUNO 154845-157726. Last production model in the United States. 186 builtVH-46F : VIP transport helicopter.CH-46X : Also known as the Boeing Model 360, this Advance Technology Demonstrator from the 1980s never entered production. The aircraft relied heavily on composites for its construction and had a beefier drive train to handle the twin Avco-Lycoming AL5512 engines (4200shp).

Canadian versions

CH-113 Labrador : Search and rescue version of the Model 107-II-9 for the Canadian Forces Air Command. 18 built.CH-113A Voyageur : Assault and utility transport version of the Model 107-II-9 for the Canadian Forces. 12 built.